Low-tech, radiative and recyclable plastic foil is considered for the passive collection of dew water. Fashioning micro-grooves at its surface by hot embossing improves by a large factor the collection of even tiny water drops. We show that this improvement is conserved under harsh outdoor conditions. The ability of the micro-grooved foil to collect condensed water is measured by the latency time tl to collect the first drop at the bottom of a vertical substrate. Compared to the same, smooth foil, tl is smaller for the micro-grooved foil by an order of magnitude. Under severe outdoor conditions (dust storm, heat wave) the properties of the micro-grooved foil are preserved after 6 months whereas the collection properties of the smooth foil have decreased by 50%. The basic reason is the insensitivity of the water collection mode to the evolution of the surface wetting and roughness properties. Such low cost, scalable and robust material should find applications in passive water harvesting devices to supply supplementary fresh water in regions where water is, or is becoming, a scarce resource.